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VIETNAM: Saltwater Intrusion Adds to Water Woes

By Tran Dinh Thanh Lam
http://www.ipsnews.net/news.asp?idnews=47205

MEKONG DELTA, Vietnam, Jun 13 (IPS) - When they got out of bed one
morning in April this year, the residents of Vi Thanh City here in
southern Vietnam’s Mekong Delta were surprised to find that their
water had become salty.

During the night, seawater had intruded into the Xa No canal, the main
source of water for the city of 200,000 people.

"Never in my life have I seen the water at Vi Thanh become that
salty," said 76 year-old Nguyen Duc Bon, who was born in the city.
"Our running water has become so salty that we could not use it for
cooking or for washing."

For daily use, inhabitants now have to buy fresh water supplied from
the nearby regional centre of Can Tho at high prices.

A dam is being built to prevent the penetration of saltwater, but it
will not be finished until 2011.

The area’s farmers also worry that their 37,000 hectares of paddies
and aquaculture could be totally destroyed by the seawater intrusion.

Many factors are being blamed for the change in water quality -
hydropower construction upstream on the Mekong River, global warming,
and, ironically, the network of small dams build by local farmers
themselves to protect their crops and aquaculture products.

There are two seasons in the Mekong Delta, the dry season, usually
taking place from May to November; and the rainy season, from December
to April.

During the dry season, the water level of the Mekong is very low,
enabling the intrusion of saltwater.

During the rainy season, the Mekong overflows, flooding the delta but
also washing out the areas recently invaded by seawater.

To fight these floods, local farmers have built a network of dams to
protect their crops and aquaculture products - a method that in
previous years was acclaimed as an innovation because it helped
farmers continue producing even in the rainy season. Now, however,
these dams have turned out to be one of the causes of saline
intrusion.

"Because of these closed dams, the overwhelming quantity of flooding
water is not retained [in the soil] and thus runs out into the sea,"
said Le Van Banh, president of the Mekong Delta Institute of Rice.
"When the dry season comes, the small quantity of underground water
that remains is not enough to stem the invading seawater."

With global warming, April and May have become the hottest months of
the dry season -at a time when the Mekong’s level of water is at its
lowest.

This has resulted in further seawater intrusion into the dried-out
regions of the Delta.

According to experts, seawater intruded up to 70 kilometres into some
parts of the Delta during the 2009 dry season - the farthest distance
in the last 20 years. More than 20,000 hectares of crops throughout
the Delta have been immersed in saltwater.

"The areas covered by sea water extend year by year," Vu Anh Phap, of
the Institute for the Development of the Mekong Delta, told Radio
France International in an interview. "The salinity is also
increasing."

Phap said that due to intensive irrigation in the Mekong region in the
past few years, especially by farmers in upstream countries like Laos
and Cambodia, the water level downstream has gone lower and lower and
allowed greater penetration of seawater.

Increasing dam construction projects upstream is also widely viewed as
another major cause of the water shortages downstream.

"These dams have reduced the water flow of the Mekong significantly,"
said Ky Quang Vinh, head of the Centre for Natural Resources and
Environment in Can Tho.

"Water shortage has already occurred this year and will be more
critical in the coming years," added Vinh. "Even in time of floods,
the water flow of the Mekong in downstream has also been reduced."

In October, he said, it fell from 40,000 cubic metres a second to
28,000 cubic metres a second.

The shortage of water in the Mekong emerged as a matter of significant
public concern in Vietnam in late May after the newspaper ‘Tuoi Tre’
cited a United Nations report saying that dams built by China on the
upper reaches of the Mekong could have significant implications for
Vietnam.

The report stated: "China’s extremely ambitious plan to build a
massive cascade of eight dams on the upper half of the Mekong River,
as it tumbles through the high gorges of Yunnan Province, may pose the
single greatest threat to the river." It went on to say the impacts of
the proposed dam development could include "changes in river flow
volume and timing, water quality, deterioration and loss of
biodiversity."

These dam developments include the recently completed Xiaowan dam,
which at 292 metres is the world’s tallest and has a reservoir storage
capacity equal to all the other Southeast Asia reservoirs combined.

It is part of China’s long-term plan to direct water for irrigation
and hydropower to dry areas of the country.

"Dams are already big at heights of 15 metres, and 292 metres is
unbelievable," Vinh told ‘Tuoi Tre’.

"[Chinese] dam construction now joins hands with climate change to
worsen droughts, salinity intrusion, landslides and land erosion," Ngo
Dinh Tuan, chair of the scientific council of the South-east Asia
Institute of Water Resource and Environment, told ‘Tuoi Tre’.

"The Vietnamese government must create a national strategy for
protecting the river downstream, not only for the Mekong but the Red
River [in Vietnam’s north], as China has started to build dams on it
as well," Tuan added.

The U.N. report also found increasingly low water levels at several
river basins such as Tonle Sap in Cambodia, Nam Khan in Laos and
Sekong-Sesan in Cambodia and Vietnam.

 
 

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